Functionalized UiO-66 induces shallow electron traps in heterojunctions with InN for enhanced photocathodic water splitting.

Indium nitride (InN) exhibited significant potential as a photoelectrode material for photoelectrochemical (PEC) water splitting, attributed to its superior light absorption, high electron mobility, and direct bandgap. However, its practical application was constrained by rapid carrier recombination occurring within the bulk and at the surface. To address these limitations, researchers developed InN/UiO-66 heterojunction photoelectrodes, which markedly enhanced PEC water splitting for hydrogen production. Functionalization of the UiO-66 metal-organic framework (MOF) with hydroxyl (-OH) groups optimized the bandgap and improved light absorption, facilitating efficient charge separation and transfer processes. The functionalization also mitigated surface defect states in the InN nanorods (NRs), which were a major source of photogenerated carrier recombination, thereby enhancing overall photocatalytic activity. Compared to pristine InN NRs, the optimized InN/UiO-66-(OH) electrode achieved a photocurrent density of -0.42 mA cm and an applied bias photon-to-current efficiency (ABPE) of 0.47 % at -0.5 V vs. reversible hydrogen electrode (RHE). Furthermore, the InN/Ag/UiO-66-(OH) system demonstrated a hydrogen production rate of 1.82 μmol min under AM 1.5G illumination, with excellent long-term stability. This study provided critical insights into the design of efficient and durable PEC photoelectrodes, achieved the highest hydrogen yield reported for indium-based photocathodes to date, and underscored the promise of InN-based materials for solar-driven hydrogen production in the context of clean energy applications.